A vehicle controlling apparatus disclosed in JP2005088834A includes a suspension control device and a navigation device. The navigation device determines that the vehicle is driven on a winding road that has, for example, two curves (e.g., a previous curve and a current curve) including a straight portion therebetween, based on electronic map data, and the suspension control device controls a suspension on the basis of the determination of the navigation device. In his configuration, even when the navigation device determines that the vehicle is driven on the straight portion, the suspension is controlled. In the light of this configuration, it is conceivable that a side support portion may be controlled in the same manner as the suspension being controlled by the vehicle controlling apparatus. As a result, an occupant of the vehicle seat may not feel frequent actuations of the supporting operation.
However, if the side support portion is controlled in the same manner as the suspension control by the vehicle controlling apparatus, when the vehicle does not have the navigation device, or when the vehicle having the navigation device is driven on a road where a GPS sensor of the vehicle does not receive signal correctly, the side support portion may not be controlled appropriately.
On the other hand, a seat apparatus for a vehicle disclosed in JP2750943 is well known. When vehicle lateral accelerations are continuously detected, the seat apparatus determines that the vehicle is driven on a road having plural curves, such as a winding road, and then a supporting operation is executed. During the supporting operation, the seat apparatus is controlled in order to retain a side support portion to a position where a human body is supported thereby (hereinbelow, referred also to as a supporting position). According to the seat apparatus disclosed in JP2750943, the side support portion is retained to the supporting position without depending on an electronic map data. As a result, an occupant of the vehicle seat may not feel frequent actuations of the supporting operation.
However, because the seat apparatus disclosed in JP2705943 determines that the vehicle is driven on the winding road when the lateral acceleration is continuously generated at the vehicle for a certain time period, even when it is determined that the vehicle is driven on another winding road, the seat apparatus may or may not continuously retain the side support portion to the supporting position when a vehicle speed varies.
A need thus exists for a seat apparatus for a vehicle which is not susceptible to the drawback mentioned above.